The cytochrome ba complex from the thermoacidophilic crenarchaeote Acidianus ambivalens is an analog of bc(1) complexes.
A novel cytochrome ba complex was isolated from aerobically grown cells of the thermoacidophilic archaeon Acidianus ambivalens. The complex was purified with two subunits, which are encoded by the cbsA and soxN genes. These genes are part of the pentacistronic cbsAB-soxLN-odsN locus. The spectroscopic characterization revealed the presence of three low-spin hemes, two of the b and one of the a(s)-type with reduction potentials of +200, +400 and +160 mV, respectively. The SoxN protein is proposed to harbor the heme b of lower reduction potential and the heme a(s), and CbsA the other heme b. The soxL gene encodes a Rieske protein, which was expressed in E. coli; its reduction potential was determined to be +320 mV. Topology predictions showed that SoxN, CbsB and CbsA should contain 12, 9 and one transmembrane alpha-helices, respectively, with SoxN having a predicted fold very similar to those of the cytochromes b in bc(1) complexes. The presence of two quinol binding motifs was also predicted in SoxN. Based on these findings, we propose that the A. ambivalens cytochrome ba complex is analogous to the bc(1) complexes of bacteria and mitochondria, however with distinct subunits and heme types.
Bandeiras
Tiago M
TM
Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República -EAN, 2780-157 Oeiras, Portugal.
Refojo
Patricia N
PN
Todorovic
Smilja
S
Murgida
Daniel H
DH
Hildebrandt
Peter
P
Bauer
Christian
C
Pereira
Manuela M
MM
Kletzin
Arnulf
A
Teixeira
Miguel
M
D041541:Acidianus / Q000378:metabolism*; D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics; D003573:Cytochrome b Group / Q000737:chemistry* / Q000235:genetics; D003575:Cytochromes c1 / Q000737:chemistry*; D014450:Electron Transport Complex III / Q000737:chemistry* / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D009876:Operon; D010084:Oxidation-Reduction; D010802:Phylogeny; D013059:Spectrum Analysis, Raman
D019843:Archaeal Proteins; D003573:Cytochrome b Group; D003575:Cytochromes c1; D014450:Electron Transport Complex III